Elimination of the Emerging Contaminants Amitriptyline Hydrochloride, Methyl Salicylate, and 2-Phenoxyethanol in Ultrapure Water and Secondary Effluents by Photolytic and Radicalary Pathways

Chemical degradation of the pharmaceuticals and personal care products (PPCPs) amitriptyline hydrochloride, methyl salicylate, and 2-phenoxyethanol by means of several advanced oxidation processes, including 254 nm UV radiation and Fenton's reagent, has been studied in different water matrixes, such as ultrapure (UP) and surface waters and two secondary effluents from wastewater treatment plants. The influence of the operating variables on the elimination of these compounds in UP water was established, and kinetic parameters for their degradation, such as quantum yields along a pH range of 3-11 and second-order rate constants for their oxidation by hydroxyl radicals, were determined. Specifically, for the reactions of oxidation of the three PPCPs with hydroxyl radicals, the use of a competition kinetic model in Fenton's reagent experiments allowed evaluation of their rate constants, whose values were (10.3 +/- 0.3) X 10(9) M-1.s(-1) for amitriptyline hydrochloride, (7.1 +/- 0.1) x 10(9)M(-1).s(-1) for methyl salicylate, and (4.3 +/- 0.1) X 10(9) M-1.s(-1) for 2-phenoxyethanol. Furthermore, the simultaneous oxidation of these selected PPCPs in three different water systems (surface water from a reservoir and two secondary effluents) was studied, and the influence of the operating conditions on the removal efficiency was established. Finally, a kinetic model was proposed for the prediction of the elimination of these compounds by UV radiation and a UV/H2O2 system in these water matrixes, with theoretical results that agreed well with the experimental ones.